CNH: Competing Demands and Future Vulnerability of Groundwater: Drinking Water Quality and Food Security in Arsenic-Impacted South and Southeast Asia

全世界数以亿计的人因饮用未经处理的地下水而暴露于危险的砷水平。砷污染会给人类带来各种严重的健康问题，包括几种形式的癌症和婴儿死亡率的增加。最近的实地证据表明，人类活动会如何提高砷的浓度，并表明在未来几十年里，会有更多的人受到影响。为大城市供水和水稻灌溉而大量抽取地下水可能会污染目前砷含量较低的深层含水层，因为抽取的地下水中砷含量很高。此外，高砷地下水灌溉显著降低水稻作物产量，威胁粮食安全。受影响地区的地下水污染程度是由个别农民的做法和大型市政当局的决定共同决定的。为了研究这些相互作用，研究人员将模拟人类决策如何影响三个经历不同程度发展的河流流域含水层中的砷水平。这项研究将确定减少地下水和水稻作物中砷含量的有效措施，从而使食品和水供应更安全。含水层的脆弱性将通过跟踪1950年至1970年期间水中氢的放射性同位素的渗透以及相对于地下水中的砷释放到大气中的碳来评估。几百口井分布在3个30公里的横断面上，其中一些受到市政和灌溉抽水的影响，而另一些则没有，将对这些和其他示踪剂进行采样。这些测量将与地下水流动和砷运移的模拟相结合，以确定灌溉抽水还是市政抽水构成更严重的威胁。农民行为将通过一项随机对照试验进行评估，在一些村庄提供实地测量灌溉用水和稻田土壤砷含量的工具包，而在其他村庄则不提供。目前，研究地区的所有稻农都使用一些肥料来提高产量，但几乎没有农民在施肥和提高产量之前去除污染最严重的表土来减少砷。研究人员将研究短期收益和长期收益之间的权衡，其中一次性投资成本与未来收益的不同模式相匹配。预计这些观测结果将证明，去除土壤和降低灌溉水中砷的含量将增加水稻产量，并保护深层低砷地下水供饮用。更广泛地说，这项研究有望为决策者提供证据，证明扩大采用简单的替代方法可以保护地下水含水层。

Hundreds of millions of people worldwide are exposed to dangerous arsenic (As) levels by drinking untreated groundwater. As contamination causes a variety of severe health problems in humans, including several forms of cancer and increased infant mortality Recent field evidence shows how human activities can elevate As concentrations and suggests many more people could be affected in the coming decades. Massive groundwater pumping for the supply of both megacities and rice irrigation could contaminate deep aquifers that currently have low levels of As, by drawing in groundwater that is high in As. Furthermore, irrigation with high-As groundwater markedly reduces the yield of rice crops, threatening food security. The extent of groundwater contamination in affected areas is determined by a combination of individual farmers' practices and the decisions made by large municipalities. In order to study these interactions, the researchers will model how human decisions affect As levels in aquifers across three river basins that have experienced differing degrees of development. The study will identify effective measures to reduce the amounts of As in groundwater and rice crops, leading to safer food and water supplies. Aquifer vulnerability will be assessed by tracking the penetration of the radioisotopes of hydrogen in water and carbon released to the atmosphere between 1950 and 1970 relative to As in groundwater. Several hundred wells distributed along three 30 km transects, some affected by municipal and irrigation pumping and others not, will be sampled for these and additional tracers. These measurements will be combined with modeling of groundwater flow and As transport to determine whether irrigation pumping or municipal pumping poses a more serious threat. Farmer behavior will be assessed through a randomized controlled trial by providing field-kits for measuring As in irrigation water and paddy soil in some villages and not in others. Currently all rice farmers in the study area use some fertilizer to boost yields, but almost no farmer removes the most contaminated topsoil to reduce As before adding fertilizer and increase yields for years to come. The researchers will examine the tradeoff between a short-term gain and a long-term gain where the one-time investment cost is paired with varying patterns of future benefits. The observations are expected to establish that soil removal and lowering of As in irrigation water will increase rice yields and protect deep low-As groundwater for drinking. More broadly, the research is expected to provide evidence for policy makers that scaling up the adoption of simple alternative approaches can protect groundwater aquifers.